The only unknown thing for me is bootX (working on a diskless, screenless
VME Board), I will have a look in the docs...

don't use BootX on G4's its not reliable at all, use yaboot instead,
much better way to go.

when partitioning with pdisk (or whatever debian calls it) create a
800K partition type Apple_BootStrap this will hold the yaboot
bootloader, the special type prevents macos from `helpfully' mounting
it and then screwing it up when it sees its not real macos.